1. Field of the Invention
The present invention relates to a technology for detecting an occurrence of a head slap in a storage device.
2. Description of the Related Art
Sometimes, shocks are undesirably applied to a magnetic disk device while the magnetic disk device is operating. Various techniques have been proposed for detecting such shocks. One such technique includes detecting the shock with a shock sensor. It is known that the degree of the shock varies depending on the cause of the shock and the environmental condition. Particularly, a shock that affects a floating condition of a head (a unit that reproduces and records of data from and to a disk) and a relationship between the disk and the head is called a “head slap”. The head slap is a shock that causes the head to slap a surface of the disk. Through an operation of detecting a shock, information related to the degree of the shock, with which the occurrence of the head slap can be determined, is to be used, for example, for determining how and under what environmental condition a user has been using the magnetic disk device.
When the shock sensor detects a shock, a control is provided to inhibit a write operation (recording operation) on a disk. To detect a shock accurately, the sensitivity of the sensor is set as high as possible. However, with a shock sensor it is difficult to determine whether the shock is a head slap or some other shock.
Japanese Patent Application Laid-open No. H7-6487 has disclosed a technology for detecting whether the shock is a head slap. This publication proposes to use detection data reproduced by a magnetic head that is not used for reproducing and recording of data. According to the disclosed technology, a magnetic head that is not used for reproducing and recording of data in a magnetic disk device is selected, and then the detection data reproduced by the exclusive magnetic head is compared with a predetermined reference value to determine whether a shock is applied to the magnetic disk device. Namely, the occurrence of a head slap can be detected by, for example, determining how much the value of the detection data exceeds the reference value.
However, with the conventional technology, there still is a problem that the process of detecting the occurrence of a head slap is complicated, and therefore, there is a threat that accuracy of the detection of a head slap is to be lowered. Specifically, with the conventional technology, it is required to select a magnetic head that is not used for reproducing and recording of data in the magnetic disk device, resulting in making the process of detecting the occurrence of a head slap complicated. Further, because the detection data used for data comparison is reproduced by the magnetic head that is different from a head used for reproducing and recording of data in the magnetic disk device, the accuracy of detecting the occurrence of a head slap gets lowered.